The following relates generally to wireless communication, and more specifically to telephone calls via a wireless communication device, such as VoLTE (voice over Long Term Evolution). Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include code-division multiple access (CDMA) systems, time-division multiple access (TDMA) systems, frequency-division multiple access (FDMA) systems, and orthogonal frequency-division multiple access (OFDMA) systems.
Generally, a wireless multiple-access communications system may include a number of base stations, each simultaneously supporting communication for multiple mobile devices. Base stations may communicate with mobile devices on downstream and upstream links. Each base station has a coverage range, which may be referred to as the coverage area of the cell.
Typically an LTE evolved Node B (eNB) implements an RRC (radio resource control) connection release mechanism based on user traffic, where a user equipment (UE) receives an RRC connection release instruction to transition from connected to idle mode. Usually user activity is tracked by the eNB, and when the UE is not active for certain amount of time (e.g., elapse of a connection release inactivity timer), the eNB will release the connection. The RRC connection release timer implemented in the eNB may be optimized with the loading, where the eNB with high loads tends to have shorter RRC connection release timers.
During IMS (IP Multimedia Subsystem) call setup (e.g., for a VoLTE call), the end-to-end call setup may take typically 4-8 sec. This time may be longer or shorter based on many factors and possible occurrence of network delays. One example that may lengthen the call setup time is the user interaction to answer the call, where the ringing process may take a few seconds.
Also in congested networks, such as in crowded venues and stadiums, high loading on the eNB may result in delaying the required radio resources to proceed with call setup. Such delays may result in a lapse of the RRC connection release timer prior to establishing the VoLTE call. When that happens, the UE will need to re-establish RRC connection to proceed with the call (and may even require the call setup procedure to be restarted). Re-establishing the RRC connection (and/or restarting the call setup procedure) results in additional delays and extra resource usage.